The invention pertains generally to multipoint electronic fuel injection systems which are sequentially actuated and is particularly directed to a single sensor actuation timing apparatus for providing control signals containing timing and steering information synchronized to each individual injector.
In a sequential fuel injection system for an internal combustion system the "trigger" or actuating control signal needs to carry at least two types of information. The primary information the control signal must carry is the actual timing of the injector actuation and secondarily information must be contained for steering that injection signal to the proper cylinder of the engine.
In such a system actuation must be initiated for successive cylinders after so many degrees of crankshaft rotation; for example, every 90.degree. of rotation in the case of an eight cylinder engine. After this injection timing information is developed it must then be steered to the proper cylinder in the sequential firing order of the system. This fact implies that the steering information must also be related to crankshaft rotation.
One technique is to provide steering information to synchronize the injection on a pulse immediately following a reference pulse indicating a selected cylinder and then rely on a ring counter to distribute the injection pulses that follow to the proper injectors according to the engine's firing order.
U.S. Pat. No. 3,809,029 issued to Wakamatsu et al. discloses an ignition and fuel injection timing system. A portion of the system consists of a means for obtaining fuel injection timing and steering information. One sensor is provided for each cylinder to obtain the fuel injection information. The circuit which controls the triggering of any one injector receives signals from the other two of the sensors. Sensible elements of a disk connected to the camshaft of the engine are sensed when the sensible elements include a reference element having a width different from the nonreference element. All of the elements are separated by equal spaces. The triggering of each individual injector is initiated by the passage of the reference element under the sensor associated with that injector. The nonreference elements function as countable items to obtain appropriate phase shifts in triggering. An electrical integrator and a comparator produce a reference or sync pulse.
Another system is described in my cross referenced application where I disclose a single sensor timing apparatus for providing steering and timing control signals. Described therein is a rotatable element having a plurality of like sensible elements which are equally spaced around a rotating member. Another sensible element located on the rotating member defines a reference element which has a recognizable geometric characteristic distinguishing it from the other sensible elements. Additionally, the spacing between the reference element and an adjacent element defines a predetermined distance different than the distance between any two adjacent nonreference elements.
Although my previous system provides steering and actuation information with a single sensor, synchronization of the sequential cycle of the system occurs only once every two engine revolutions. This technique can create difficulty in starting an internal combustion engine particularly when an extremely fast and emission free start is desirable.
Waiting two engine revolutions for the timing and steering control to synchronize will produce delays that are unacceptable in the starting operation of an internal combustion engine especially at colder temperatures. At 0.degree. F. the cranking speed of the engine may slow to 60 rpms and at colder temperatures, -20.degree. F. for example, may drop to as low as 30 rpms. Respectively, this could introduce a delay as long as two seconds and four seconds before synchronization can occur. Fuel is not injected into the engine during this time thereby unduly lengthening the starting time. Fuel cannot be injected before synchronization because the electronics may initialize in an incorrect signal sequence. If this happens the double injection of a cylinder is possible with a resulting start that is laden with high emissions.
Therefore, in a sequential multipoint system it would be advantageous to provide an actuation timing apparatus which would positively identify the engine position of the next injector to be actuated by synchronizing on each injector.